Low angle X-ray diffraction will be used to determine the molecular arrangements in various connective tissues, containing different genetic types of collagen and different non-collagenous components, and also to examine the molecular organization in oriented gels of reprecipitated purified collagen solutions. The 670 Angstrom meridional reflections will be used to obtain information on the axial structure in collagen fibrils, and the equatorial reflections will be used to investigate the lateral order. Electron microscopy will be done on all specimens, both to check their integrity and to help interpret the X-ray data. Such studies should allow one to define the different arrangements of collagen molecules in various tissues and in diseased states, and to understand these different arrangements in terms of the genetic types of collagen and the presence of non-collagenous components.